1. Define the relationship of the tendinous arch to the obturator internus muscle and levator ani.
The tendinous arch is a thickening of the fascia of the obturator internus muscle on the lateral aspect of the pelvic outlet. Laterally, it forms the pudendal canal in the ischioanal fossa region. This tendinous arch traverses between the ischial spine of the pelvis to the anterior portion of the inferior ramus of the pubis, and serves as the muscle attachments for some of the muscles of the pelvic diaphragm, including coccygeous laterally and levator ani anteriorly.(See below)
Levator ani is comprised of two muscles (or three if you count the sling):
-Pubococcygeous, which runs between the pubis and the coccyx, and has a component that surrounds the rectum called puborectalis;
-Iliococcygeous, whose fibers run between the inferior portion of the ilium and the coccyx.
Coccygeous runs mediolaterally on either side of the coccyx to the ischial spine, and is sometimes known as Ischiococcygeous.
2. Explain the difference in orientation of the pelvic and urogenital diaphragms.
The pelvic diaphragm is made up of the ischiococcygeus, pubococcygeus, and iliococcygeus muscles and is oriented in a funnel shape, with the convex side facing inferiorly. The fibers of the pubococcygeus that don’t attach to the coccyx meet up to form a sling called the puborectalis muscle that pulls the anal-rectal junction towards the pubis.
The deep pouch is a potential space and is part of the the urogenital diaphragm. There are 2 gaps for the deep dorsal nerve, and for the urethra. The urogenital diaphragm is on a different plane than the pelvic diaphragm and stretches horizontally to the pubic rami on either side inferior to the pelvic diaphragm when viewed superiorly. Together, they close the pelvic outlet.
3. Define the parts of the pelvic diaphragm/urogenital diaphragm.
Obturator internis fascia has a thickening of the fascia that runs from the pubis to the ischial spine called the tendonous arch. The tendonous arch proves attachments to muscles in the pelvic diaphram. Fibers in the pelvic diaphram that attach from the pubis to the coccyx is called the pubococcygeus muscle. Fibers from the tendenous arch to the coccyx is called the iliococcygeous muscle. These two muscles are not really separate and make up the levator ani muscle. Deep in the pelvis, parallel with piriformis, and attaching from the ischiospine to the coccyx, is called the ischiococcygeus or the coccygeus muscle. The ischiococcygeus, pubococcygeus, and iliococcygeus make up the pelvic diaphragm. The fibers of the pubococcygeus that don’t attach to the coccyx meet up to form a sling called the puborectalis muscle that pulls the anal-rectal junction towards the pubis.
Between the two parts of the pubococcygeus muscle on the pubis, there is a gap in the pelvic floor that is closed by the genital hiatus that is closed by the urogenital diaphragm. The urogenital diaphragm is the perineal membrane, the muscles of the deep pouch, and the fascia on the superior ascpect of the deep pouch (which is muscular fascia). Therefore, the deep pouch is a potential space and is part of the the urogenital diaphragm.
4. Describe the relationship of the parts of levator ani to pelvic organs.
Obturator internis fascia has a thickening of the fascia that runs from the pubis to the ischial spine called the tendonous arch. The tendonous arch proves attachments to muscles in the pelvic diaphram. Fibers in the pelvic diaphram that attach from the pubis to the coccyx is called the pubococcygeus muscle. Fibers from the tendenous arch to the coccyx is called the iliococcygeous muscle. These two muscles are not really separate and make up the levator ani muscle.
5. Describe the nerve supply to levator ani.
Levator ani muscles are supplied by the nerve to levator ani, which comes from the ventral ramii of S4 of the coccygeal plexus. Some innervation may also be derived from the pudendal nerve (S2-4) via the inferior rectal nerve.
6. Describe the branching pattern of the internal iliac artery.
The internal iliac gives off two main branches, commonly known as the anterior and posterior branch.
The anterior division gives rise to several branches. The obturator artery exits the pelvis and goes down to the medial thigh and is paired with the obturator nerve through the obturator foramen. The patent portion of the umbilical artery comes off the anterior division and gives off the superior vesticle arteries, before being fibrous and reflecting into the anterior abdominal wall as the median fold. In the female, a vaginal branch goes to the vagina. The uterine artery branches off the vaginal artery and crosses superior to the ureter. The inferior vesticle artery branches off the anterior internal iliac in the male, but in females, it is believed not to exist. The middle rectal artery is a small branch, contributing to the anastomosis with the superiorectal artery. The inferior gluteal and the internal pudendal artery are the major branches of the anterior division of the internal iliac; these two arteries both leave the pelvis.
The posterior division branches into 3 arteries. The iliolumbar artery branches from the posterior division of the internal iliac and ascends back into the false pelvis along the lumbar vertebrae, supplying blood to the muscles on the false pelvis. The lateral sacral arteries travel to the lateral aspect of the sacrum, supplying the sacral plexus, piriformis, and to the terminal portions of the spinal cord (cauda equina). The superior gluteal is the largest branch that leaves the pelvis via greater sciatic foramen between the lumbosacral trunk and S1.
Anterior Branches:
(O)-The obturator artery to the obturator canal;
(IG)-The inferior gluteal artery through the greater sciatic foramen;
(The uterine artery (or deferential artery in males) to the uterus or vas deferens;
The vaginal artery(or the vesicular artery in males) to the vagina in females or urinary bladder in males;
(MFC)The middle rectal artery to the rectum; and
(IP)-The internal pudendal artery
Posterior Branches:
(IL)-The iliolumbar artery (iliac and lumbar branches) supply psoas major, iliacus, and quadratus lumborum;
(LS)-The Lateral Sacral arteries, through the anterior sacral foramina;
(SG)-The superior gluteal artery, through the greater sciatic foramen.
7. Describe the distribution of the branches of the sacral plexus.
There is a somatic nerve plexus formed by the ventral rami of the spinal nerves S1-S5. These nerves plus the lumbosacral trunk from the lumbar plexus form the sacral plexus. Primary innervation from the sacral plexus is into the lower limb. The pudendal nerve also comes out of the sacral plexus and contains contributions from S2-S4. The piriformis muscle forms the posterior wall behind the sacral plexus.
Table of Contents
Pelvis Walls and Floor - Lecture Notes
Lecture 1
Pelvis Walls and Floor
1. Define the relationship of the tendinous arch to the obturator internus muscle and levator ani.
The tendinous arch is a thickening of the fascia of the obturator internus muscle on the lateral aspect of the pelvic outlet. Laterally, it forms the pudendal canal in the ischioanal fossa region. This tendinous arch traverses between the ischial spine of the pelvis to the anterior portion of the inferior ramus of the pubis, and serves as the muscle attachments for some of the muscles of the pelvic diaphragm, including coccygeous laterally and levator ani anteriorly.(See below)
Levator ani is comprised of two muscles (or three if you count the sling):
-Pubococcygeous, which runs between the pubis and the coccyx, and has a component that surrounds the rectum called puborectalis;
-Iliococcygeous, whose fibers run between the inferior portion of the ilium and the coccyx.
Coccygeous runs mediolaterally on either side of the coccyx to the ischial spine, and is sometimes known as Ischiococcygeous.
2. Explain the difference in orientation of the pelvic and urogenital diaphragms.
The pelvic diaphragm is made up of the ischiococcygeus, pubococcygeus, and iliococcygeus muscles and is oriented in a funnel shape, with the convex side facing inferiorly. The fibers of the pubococcygeus that don’t attach to the coccyx meet up to form a sling called the puborectalis muscle that pulls the anal-rectal junction towards the pubis.
The deep pouch is a potential space and is part of the the urogenital diaphragm. There are 2 gaps for the deep dorsal nerve, and for the urethra. The urogenital diaphragm is on a different plane than the pelvic diaphragm and stretches horizontally to the pubic rami on either side inferior to the pelvic diaphragm when viewed superiorly. Together, they close the pelvic outlet.
3. Define the parts of the pelvic diaphragm/urogenital diaphragm.
Obturator internis fascia has a thickening of the fascia that runs from the pubis to the ischial spine called the tendonous arch. The tendonous arch proves attachments to muscles in the pelvic diaphram. Fibers in the pelvic diaphram that attach from the pubis to the coccyx is called the pubococcygeus muscle. Fibers from the tendenous arch to the coccyx is called the iliococcygeous muscle. These two muscles are not really separate and make up the levator ani muscle. Deep in the pelvis, parallel with piriformis, and attaching from the ischiospine to the coccyx, is called the ischiococcygeus or the coccygeus muscle. The ischiococcygeus, pubococcygeus, and iliococcygeus make up the pelvic diaphragm. The fibers of the pubococcygeus that don’t attach to the coccyx meet up to form a sling called the puborectalis muscle that pulls the anal-rectal junction towards the pubis.
Between the two parts of the pubococcygeus muscle on the pubis, there is a gap in the pelvic floor that is closed by the genital hiatus that is closed by the urogenital diaphragm. The urogenital diaphragm is the perineal membrane, the muscles of the deep pouch, and the fascia on the superior ascpect of the deep pouch (which is muscular fascia). Therefore, the deep pouch is a potential space and is part of the the urogenital diaphragm.
4. Describe the relationship of the parts of levator ani to pelvic organs.
Obturator internis fascia has a thickening of the fascia that runs from the pubis to the ischial spine called the tendonous arch. The tendonous arch proves attachments to muscles in the pelvic diaphram. Fibers in the pelvic diaphram that attach from the pubis to the coccyx is called the pubococcygeus muscle. Fibers from the tendenous arch to the coccyx is called the iliococcygeous muscle. These two muscles are not really separate and make up the levator ani muscle.
5. Describe the nerve supply to levator ani.
Levator ani muscles are supplied by the nerve to levator ani, which comes from the ventral ramii of S4 of the coccygeal plexus. Some innervation may also be derived from the pudendal nerve (S2-4) via the inferior rectal nerve.
6. Describe the branching pattern of the internal iliac artery.
The internal iliac gives off two main branches, commonly known as the anterior and posterior branch.
The anterior division gives rise to several branches. The obturator artery exits the pelvis and goes down to the medial thigh and is paired with the obturator nerve through the obturator foramen. The patent portion of the umbilical artery comes off the anterior division and gives off the superior vesticle arteries, before being fibrous and reflecting into the anterior abdominal wall as the median fold. In the female, a vaginal branch goes to the vagina. The uterine artery branches off the vaginal artery and crosses superior to the ureter. The inferior vesticle artery branches off the anterior internal iliac in the male, but in females, it is believed not to exist. The middle rectal artery is a small branch, contributing to the anastomosis with the superiorectal artery. The inferior gluteal and the internal pudendal artery are the major branches of the anterior division of the internal iliac; these two arteries both leave the pelvis.
The posterior division branches into 3 arteries. The iliolumbar artery branches from the posterior division of the internal iliac and ascends back into the false pelvis along the lumbar vertebrae, supplying blood to the muscles on the false pelvis. The lateral sacral arteries travel to the lateral aspect of the sacrum, supplying the sacral plexus, piriformis, and to the terminal portions of the spinal cord (cauda equina). The superior gluteal is the largest branch that leaves the pelvis via greater sciatic foramen between the lumbosacral trunk and S1.
Anterior Branches:
(O)-The obturator artery to the obturator canal;
(IG)-The inferior gluteal artery through the greater sciatic foramen;
(The uterine artery (or deferential artery in males) to the uterus or vas deferens;
The vaginal artery(or the vesicular artery in males) to the vagina in females or urinary bladder in males;
(MFC)The middle rectal artery to the rectum; and
(IP)-The internal pudendal artery
Posterior Branches:
(IL)-The iliolumbar artery (iliac and lumbar branches) supply psoas major, iliacus, and quadratus lumborum;
(LS)-The Lateral Sacral arteries, through the anterior sacral foramina;
(SG)-The superior gluteal artery, through the greater sciatic foramen.
7. Describe the distribution of the branches of the sacral plexus.
There is a somatic nerve plexus formed by the ventral rami of the spinal nerves S1-S5. These nerves plus the lumbosacral trunk from the lumbar plexus form the sacral plexus. Primary innervation from the sacral plexus is into the lower limb. The pudendal nerve also comes out of the sacral plexus and contains contributions from S2-S4. The piriformis muscle forms the posterior wall behind the sacral plexus.